Hume on Personal Identity: Who Are We?

What makes somebody the same person at one time as at another? What criteria define personhood in general? David Hume’s theory of human nature provides some fairly radical answers to both of these questions.

Hume was a philosopher working during the 18th century, a time at which the natural sciences appeared to be making ever more frequent, definite discoveries about reality. Hume wanted to apply some of the working principles of the natural sciences to the study of the human mind, and his theory of personal identity is an important element of that project.

This article begins with an explanation of what the problem of personal identity is. It then moves on to summarize Hume’s philosophical project in general, and situate his response to the problem within. The article concludes by examining a range of criticisms of Hume’s approach and evaluating the success of these criticisms.

Personal identity is often used to refer to a specific problem. The problem in question is one of how we determine what makes a person the same person at different points in their lives. This question might seem at first glance simple enough, if not downright pedantic. It is neither. This apparently discreet problem ends up bearing on a whole range of further philosophical problems, many to do with the nature of personhood or “the self.”

Hume’s theory of the self is intimately bound up in his philosophical project in general. To summarize briefly, Hume argues that given all knowledge is mediated by our nature as human beings, the first object of inquiry should be human beings themselves, and the conditions by which human beings can understand things.

In effect, Hume’s philosophy asserts that the philosophical topic we must address first is the philosophy of mind.

What he goes on to say is that there are three elements of our mind – impressions, ideas, and the procedures which govern them. Impressions are basically simple perceptions such as the experience of redness, and ideas include things as memories of perceptions, but also concepts, elements of human reason, and other more abstract parts of our mental life.

To get at the crux of the problem with personal identity, we need to recognize that Hume’s philosophy is often read as responsive to a tradition in philosophy that precedes him. This tradition, which runs from Descartes through such major philosophers as Spinoza and Leibniz, focuses on attempting to characterize substance, a metaphysical concept which – among other properties – is not subject to change even as we perceive change happening. The problem with concepts like these, as Hume observes, was that they tend to be idiosyncratic, speaking to no basis we can agree on, and so each philosopher develops their own concept of substance.

It is very important and often overlooked that at the very start of the Treatise on Human Nature, Hume’s first major philosophical work (and the work in which he addresses personal identity and selfhood), Hume complains about the discord within philosophy and draws a sharp contrast with the apparent agreement and progress he saw in the natural sciences.

Before moving on to what Hume said about personal identity specifically, it is worth noting that the very idea of personal identity is closely related to the idea of substance (or a kind of pseudo-substance, a concept that functions for all intents and purposes like a substance), in which many philosophers locate the source of the persistence we express with terms like the “soul” or the “self.”

Hume’s focus, as he clarifies, is in explaining how we come to believe in the existence of persons or selves, and the status of this belief in his conception of human nature. The first thing to note is that, given Hume’s conception of the elements of our minds, there is no such thing as an unchanging thing called the mind. In one of the most famous passages in the Treatise, Hume describes the mind as follows:

“The mind is a kind of theatre, where several perceptions successively make their appearance; pass, re-pass, glide away, and mingle in an infinite variety of postures and situations. There is properly no simplicity in it at one time, nor identity in different”

Causality and Succession: An Atomistic Conception of Mind

These successive appearances that take place in experience, and the smoothness of the transitions between them, lead to the creation of totalizing concepts of the mind. Atomistic approaches to the mind are more accurate. This is related to a certain idea Hume has about causation:

“The true idea of the human mind, is to consider it as a system of different perceptions or different existences, which are link’d together by the relation of cause and effect, and mutually produce, destroy, influence, and modify each other. Our impressions give rise to their correspondent ideas; and these ideas in their turn produce other impressions. One thought chases another, and draws after it a third, by which it is expell’d in its turn.”

On the face of it, this seems plausible – at least within the confines of Hume’s conception of the mind. Yet there are various criticisms that Hume faces. Here is one kind of criticism: as Barry Stroud explains, the novelty and lack of uniformity that we find in our inner life make it difficult to see how Hume’s appeal to resemblance and causality could possibly be enough to explain why we come to have an idea of an individual mind or self that endures through time.

Stroud notes, “it does not follow that his theory is involved in some vicious circularity because of that. It does not follow that the human subjects about whom Hume is theorizing must themselves have the idea of causality in order to get the idea of a single mind, and must have the idea of a single mind in order to get the idea of causality.”

A different line of criticism runs as followers: Hume says that we take certain perceptions and use them to develop the following concept as an explanation for their relationship. This concept is, in fact, not a good explanation, or is perhaps incoherent or chimerical. But how can Hume hold that such perceptions lead us to develop a certain concept – surely the concept isn’t necessarily implied by these perceptions, so in order to have this concept, we must acquire it in some other way.

A third criticism, which also comes from Stroud, goes as follows:

“Consider now a bundle of perceptions consisting of one of my perceptions, one of its effects, which is one of your perceptions, one of its effects, which is someone else’s, and so on. In considering such a bundle, or in contemplating a world in which perceptions came that way, would we find ourselves inclined to regard them all as constituting one mind? It seems to me that the answer is ‘No’, but it must be admitted that the speculation is so far-fetched that we hardly know what our reactions would be if it were realized.”

However, this doesn’t seem to take the natural conclusion of Hume’s argument seriously. It is an implication of Hume’s theory that we can stop making precisely this kind of judgment. All that exists are impressions, ideas, and their operations. The answer to any question such as “is there an underlying mind?”, is, in the last analysis, unimportant insofar as it fails to get at the core elements of the human mind.

We could, however, press Hume another way. In particular, we could press him to explain what is meant by “an experience.” In other words, what separates one experience from another? Is it just whatever we identify as a single moment of time? This might vary from person to person.

Of course, Hume could respond that this is really a manner of speaking, and perhaps there is no strict distinction between one experience and another. Yet, Hume often talks about the relations between experiences.  Do we not need a sense of what an experience is rather than simply experience if we wish to relate one experience to another?

Consider the following claim: “When I am having an impression of a tree I might turn my head and get an impression of a building, but the first impression is not a cause of the second”. Although I’ve suggested that the question of personal identity as such means little in Hume’s system, a whole range of further mental concepts – memory and intention are those exhibited in this example – are at risk of being totally jettisoned. It is one thing to make radical claims about the mind and human beings. It is quite another to describe the world in ways totally opposed to any available descriptions of ourselves and our minds.